Combustion apparatus



July 4, 1939. R. A. FORESMAN 2,164,510

COMBUSTION APBARATUS Filed June 14,-1935 2 Sheets-Sheet 1 Ill M O 5 6 7 I 3 a a 9 w Y ll'lTI V R E E 4 ||Ll l R v 6 I m 0 x l 7 e B N F o 4 v 4 w n 1. 6 w 6 m m m 4 m A A 7 IIIIIU/ 5 2 m m I Y s s a a a w e I R n F Q P.

' WITNESSES:

y 1939. R'. A. FORESMAN 2,164,510

COIBUSTION APPARATUS Filed June 14, 1955 2 Sheets-Shet 2 WITNESSES: INVENTOR ROBERT HrFo EsM/m v ATTORY Patented July 4, 1939 UNITED STATES PATENT OFFICE COMBUSTION APPARATUS of Pennsylvania Application June 14,

8 Claims.

My invention relates to combustion apparatus and has for an object to provide an improved method and apparatus for the combustion of solid fuels.

A further object of my invention is to provide an improved heat generating unit of the domestic type which may be operated for long periods with a minimum of attention.

Further objects of my invention are to preheat the fuel prior to its delivery to the combustion chamber, properly distribute air througout the length of the burning fuel bed, regulate the quantity of air for insuring efficient combustion, and to minimize the collection of soot or other solids on the heat transfer surfaces of the unit.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in accordance with the accompanying drawings, forming a part of this application, in which:

Fig. l is a vertical sectional View of my improved heat generating unit and is taken along the line I-I of Fig. 2;

Fig. 2 is a plan view of the apparatus of Fig. 1;

Fig. 3 is a plan view of the boiler unit;

Fig. 4 is a section taken along the line IVIV of Fig. 3;

Fig; 5 is a diagrammatic developed section of the apparatus shown in Fig. 2 looking outwardly from the combustion chamber;

Fig. 6 is a section taken along the line VIVI of Fig. l;

Fig. '7 is a view of a detail taken along the line VII-VII of Fig. 1;

Fig. 8 is a sectional view of a detail taken along the line VIII-VIII of Fig. 6; and,

Fig. 9 is a view showing a modified roof structure for the combustion chamber.

In the present application, I disclose and claim a method and apparatus for effecting combustion in a heat generator'of the character generally disclosed and claimed in my Patent No. 2,043,994, dated June 16, 1936.

Referring now to Fig. 1 of the drawings, my improved apparatus includes an upper unit or boiler I and a lower stoker unit II. The stoker includes an annular grate structure I2 rotatably mounted in a base member I3 which also supports the boiler Ii]. Included in the grate structure I2 is a frame l4 having inner and outer rings I and I6, respectively, connected by radial tie bars I7. As shown particularly in Fig. 6, complementary segmental grate members l8 are carried by the frame I4 and define a substantially horizontal, annular fuel supporting structure.

1935, Serial No. 26,600

The base I3 includes an outer wall I9 and an inner column 28 connected by radial partitions 2| and 22, whereby a pair of arcuate chambers 23 and 24 are defined. Chamber-23 constitutes a wind box and may be supplied with air for com- 6 b-ustion in any suitable manner as by an opening 25 controlled by a damper 26. Lugs 21 are-provided on the inside of the wall I9 which, in conjunction with the partitions 2| and 22, form supports for the rotatable grate structure I2.

In order that air supplied to the wind box chamber 23 may be confined to the portion of the grate disposed thereabove, seals are provided between the chambers 23 and 24. As best shown in Figs. 6 and 8, the seals may include flanges 28 and 29 arranged at the top of the partitions 2| and 22, respectively, which flanges 28 and 29 are of a width greater than the spacing of adjacent radial bars ll. With this construction, it will be apparent that, during rotation of the grate, the upper surface of the fianges 28 and 29 will always be engaged by at least one radial bar I'I, so that passage of air from the wind box 23 to the chamber 24 over the partitions 2| and 22 is prevented. The extent of the metal to metal con- 25 tact between the flanges 28 or 29 and the radial bars I! may be reduced by recessing the upper surfaces of the flanges as shown at 28a. in Fig. 8. The recess fills with fine ash which is leveled oif by the bars I l and complements the upper surface 30 of the flange to form a sealing surface.

Rotation of the grate structure I4 may be effected in any convenient manner as by means of a pawl and ratchet mechanism 3|; As shown in Fig. 7, the latter may include ratchet teeth 32 formed on the bottom of the outer frame ring it and a pawl 33, oscillated by means of a shaft 34 in any suitable manner.

The boiler unit I8 is arranged above the grate structure I4 and includes an outer jacketed wall structure 35 having a space 36 formed therein for water to be heated. Arranged substantially in coaxial relation with the outer wall 35 is an inner wall or column 31 defining a water space 38. The inner and outer wall structures 35 and 31 are joined by means of jacketed wall structures II and 42 which are circumferentially spaced, and which include, respectively, water spaces 43 and :4, communicating with the water spaces 36 and 38. The walls M and 42 divide the annular space between the inner and outer walls 35 and 31 into arcuate chambers and 46, the first of which is a fuel receiving space or magazine and the second of which defines the furnace chamber. The 5 chambers may be covered by a top wall formed of complementary segments 41.

Arranged within the furnace chamber 46 is a baffle or roof structure 48 extending from adjacent the wall 42 toward the wall 4| but terminating in spaced relation therewith. A jacketed baffie 49 extends vertically from adjacent the end of the roof 48 and terminates at its upper end in spaced relation with the top wall 41. The baffle 49 defines with the Wall 4| a vertical gas passage 5| which communicates at its bottom with a combustion chamber 52 beneath the roof structure 48. A gas outlet 5 3 communicates with the furnace chamber 46 at the end remote from the passage 5| and a tortuous path for escaping gases is provided by disposing a jacketed baffie 54 between the baffle 49 and the gas outlet 53. With this construction, vertical gas passages 55 and 56 are defined above the roof structure 48. Preferably, the jacketed b-affies 49 and 54 are part of the heat transfer surface of the boiler and are, therefore, provided with water spaces 51 connected to the spaces 36 and 38.

In operating a stoker of the type disclosed, it is necessary, for successful operation, to provide a fuel supply of substantially constant depth. This is accomplished, preferably, by spacing the bottom of the wall 4| from the grate whereby a fuel discharge opening 58 is defined. As shown in Fig. 5, fuel is delivered by any suitable means into the space 45 to a depth higher than the top of the opening 58 so that as the grate I4 is rotated, fuel will be carried from the space 45 into the combustion chamber 52 and the depth of the bed will be determined by the height of the opening 58. While fuel may be delivered continuously in any well known manner to the space 45 so that the depth of fuel therein is maintained above the top of the opening 58, I prefer to show a relatively large space in which suflicient fuel for a long period of operation may be stored. The space 45, therefore, may be considered as a fuel magazine and may be periodically filled through the top by removing the segment 41 above the magazine.

As the fuel is carried through the combustion chamber 52, it is progressively burned and the depth of the fuel bed, therefore, progressively diminishestoward the wall 42 where combustion of the fuel is complete. Ash is removed radially from the grate, preferably, by the wall 42, the bottom of which is adjacent to the grate and which functions as an ash scraper. The wall 42 is preferably arranged at a tangent to the inner wall so that movement of the ash radially of the grate is facilitated. An opening 50 is provided in the outer wall structure 35 adjacent the wall 42, through which opening 6|] the ash passes as the grate advances beneath the wall 42. A container 6| may be disposed beneath the opening '60 for the collection of ash discharged from the grate. A dust tight housing 62 having an access door 63 may be fitted to the structure for enclosing the refuse container 8|.

A sufiicient body of fuel is maintained in the space 45 at all times so that the upper level thereof is above the top of the opening 58. As the grate rotates, fuel is carried through the opening and the depth of the bed is determined by the height of the opening as stated heretofore. Ignition is effected adjacent the exit of the opening and combustion progresses as the grate advances the fuel beneath the passage 5| and the roof 48. with an incidental progressive reduction in the depth of the fuel bed. Sufiicient air for combustion is admitted to the wind box 23 through opening 25.

The pressure of the air on the under side of the active portion of the grate above the wind box 23 is substantially equal throughout the length thereof.

The body of ash formed beneath the fuel increases progressively toward the region of complete combustion but, as the space occupied by ash is less than that of the coal consumed, the upper surface of the fuel bed will be inclined as shown in Fig. 5. The resistance to the flow of air through the bed of fuel and ash therefore decreases from the fuel admission end of the bed toward the region where combustion is complete. This would cause excess flow of air to pass through the bed at the end of minimum thickness and, incidentally, a deficiency in the amount passing through the thicker end of the bed. In order to obviate this condition, I provide means within the combustion chamber for varying the pressures above the fuel bed progressively, so that the differential in pressure across the bed varies with the thickness thereof.

As best shown in Fig. 5, the gases of combustion are withdrawn through passage 5| adjacent the end of the fuel bed of maximum thickness. It is above this portion of the bed that the region of lowest pressure exists and, as the pressure beneath the fuel bed is equalized, substantially, throughout the length thereof, this represents the region of greatest pressure difference between the space above and below the fuel. The flow of gases from the opposite end of the fuel bed toward the passage 5| is restricted, so that their velocity increases and pressure decreases toward the passage 5|. There is, therefore, a progressive decrease in the pressure difference across the grate from the end of the bed of maximum depth to the end of minimum depth. The pressure differentials may be predetermined so that desired air volumes are conveyed through the fuel bed throughout its length.

The restriction of gases passing to the passage 5| is preferably obtained by so arranging the roof 48 in the chamber 46 that it defines with the fuel bed a passage which converges toward the gas passage 5|. I have shown the roof 48 disposed in a substantially horizontal plane but it will be understood that, in some designs, it may be inclined to obtain the proper convergence. It may be desirable in some cases to bleed excess air from the combustion chamber for increasing the furnace efi'iciency and, therefore, I provide a conduit 68 which connects the region of the combustion chamber 52 of highest pressure with the stack (not shown). An adjustable damper 69 is arranged in the conduit '58 for varying the amount of excess air withdrawn from the chamber 52,

Air which passes through the grate adjacent the thin and of the fuel bed is thoroughly mixed with gases in the combustion chamber for promoting combustion. The hot gases are projected into engagement with the wall 4| after issuing from the chamber 52 and pass upwardly. Combustion is completed in the passage 5| and the hot products thereof pass downwardly between the baffles 49 and 54 and then upwardly to the gas offtake 53. By directing the hot gases into contact with the wall 4|, a relatively large amount of heat is absorbed thereby, both by convection and by radiation. The fuel within the space 45 is preheated to a desirable degree and is subjected to the high temperature gases immediately 'upon issuing from the opening 58 where ignition is effected.

From the foregoing, it will be apparent that I have provided a boiler structure having heat transfer surfaces which are vertically disposed and, therefore, a collection of solids thereon which would materially affect their heat absorbing qualities is prevented. This is due to gravity and to the sweeping action of the high velocity gases passing over these surfaces. The top of the roof is the only surface presented to the gases upon which solids may collect and I have provided a plurality of restricted openings 64 therein through which the solids may sift by gravity. This action occurs especially when the draft has been shut down or at times when the upward flow of gases through the openings 64 is insufficient to suspend a dropping particle. In this connection, it will be apparent that there will be an upward flow of hot gases through these openings 64 during operation of the furnace but the flow is very small so that it does not seriously affect the efficiency of operation. I have found that a few of these openings 64 will prevent a thick collection of solids on the roof 48 due to the small angle of repose of such solids.

In the present embodiment of the invention, I have shown a roof structure of refractory material but it may be desirable to utilize a water cooled structure in some furnaces. Accordingly, in 9, I have shown a combustion chamber roof construction which forms a part of the heat transfer surface of the boiler. The View discloses a roof 55 having a water space 66 connected to the water space of the wall 42 and baiile 49. Small tubular members 61 may be arranged in the arch 65 for passing solids in the same manner as described in connection with the prior embodiment.

From the foregoing, it will be apparent that I have devised a novel mechanical heat generating unit in which a novel method of combustion is practiced, in which fuel is preheated prior to its admission to the furnace and in which furnace parts are maintained clean. The furnace disclosed employs natural draft but it will be understood that my invention contemplates the use of forced draft. Furthermore, while I have disclosed my improved combustion apparatus applied to a structure for heating water, it is to be understood that it may be applied for heating other media.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, Without departing from the spirit thereof, and I desire, therefore, that only such limitations shall beplaced thereupon as are imposed by the prior art or as are set forth in the appended claims.

What I claim is:

l. The method of burning fuel in a combustion chamber which includes admitting a bed of fuel of predetermined thickness to the chamber, progressively burning the fuel as it is advanced through the chamber so that the thickness of the fuel bed in the chamber and the resistance to the flow of air through the bed progressively diminish toward the region of complete combustion, establishing pressures in the chamber above the fuel bed which increase progressively from adjacent the portion of the fuel bed of maximum thickness toward the portion of minimum thickness, said pressures increasing proportionately as the resistance of the fuel to air flow decreases, and supplying air beneath the fuel bed at a pressure in excess of the highest pressure above the fuel bed so that the flow of air through the fuel bed is substantially uniform throughout its length.

2. In combustion apparatus, the combination of a rotatable annular grate, a furnace structure having inner and outer substantially coaxial walls arranged above the grate, and defining an annulus therebetween, a top wall connecting said inner and outer walls, first and second walls connecting said inner and outer walls and circumferentially spaced for defining a magazine for fuel and an arcuate chamber, said first wall being spaced from the grate for defining a fuel discharge opening and said second wall cooperating with the grate for deflecting ash therefrom, a substantially vertical baffle arranged in the arcuate chamber and circumferentially spaced from said first Wall, said bafiie terminating in spaced relation with said top wall and with said grate, a roof structure arranged above the grate and extending substantially from said baflle to said second circumferentially spaced wall for defining, with the grate, a combustion chamber, a second substantially vertical 'baflle connecting the inner and outer walls and spaced above the roof structure, means for rotating said grate so that fuel is conveyed through said opening and is burned progressively as it passes through the combustion chamber and means for discharging products of combustion from the arcuate chamber intermediate the second-mentioned baffle and said second circum-ferentially spaced wall.

3. The combination as claimed in claim 2 having means for discharging excess air from the combustion chamber at a point adjacent the second circumferentially spaced wall.

4. In combustion apparatus, the combination of a furnace structure having a movable grate therein, means for depositing the bed of fuel of predetermined depth upon a portion of the grate for combustion as it passes through the furnace whereby the thickness of the bed of fuel and its resistance to air fiow progressively decrease toward the region of complete combustion, means for removing ash from the grate adjacent the region of complete combustion, said furnace structure defining with the bed of fuel a combustion chamber that converges in the direction from the ash removal end of the grate to the fuel admission end thereof, means for withdrawing products of combustion from the smallest portion of the combustion chamber so that the pressures obtaining within the combustion chamber increase progressively from the portion of the fuel bed of maximum thickness towards the portion thereof of minimum thickness and inverse relation to the resistance of the fuel bed to the air flow, and means for admitting air beneath the fuel bed at a substantially uniform pressure throughout its length, said pressure exceeding the highest pressure above the fuel bed so that the pressure differentials across different regions of the fuel bed bear a predetermined relation to the resistance thereof and the flow of air through the fuel bed is optimum for the various regions thereof.

5. The combination as claimed in claim 4 including means for bleeding excess air from a portion of the combustion chamber in which the pressure is at a relatively high value.

6. In combustion apparatus, the combination of inner and outer substantially concentric walls defining an annular space therebetween, a rotatable annular grate arranged adjacent the bottom of said space, means arranged within the space for depositing fuel of a predetermined depth upon the grate, means for rotating the grate so that the fuel is progressively burned as it traverses the space and the thickness of the fuel bed progressively diminishes, means circumferentially spaced from the fuel depositing means for removing ash from the grate, a roof structure spaced above the grate and extending from adjacent the, ash removal means toward the fuel depositing means, said roof structure defining with the fuel bed a chamber that converges in a direction counter to the movement of the grate and forming a gas oiftake adjacent the fuel depositing means for gases passing through said chamber, the convergence of said passage being such that the pressure of the gases passing toward the offtake is progressively reduced, the values of the pressure in the various zones of the passage bearing a predetermined relation to the resistance of the fuel bed in the respective zones, and means for admitting air for combustion to the under side of the portion of the grate disposed within said chamber and at a substantially uniform pressure throughout the length of such grate portion.

7. The method of burning fuel in a combustion chamber which includes admitting a bed of fuel of predetermined thickness to the chamber, progressively burning the fuel as it is conveyed through the chamber so that the thickness of the fuel bed and the resistance to the flow of air through the bed progressively diminish toward the region of complete combustion, passing the products of combustion along the fuel bed from the end thereof of minimum thickness toward the end of maximum thickness and at progressively increasing velocities with'coresponding progressive decreases in pressure, said pressures decreasing proportionately as the resistance of the fuel bed to air flow increases, whereby a predetermined relation between the resistance to air flow of various portions of the fuel bed and the pressures thereabove is provided, withdrawing the products of combustion from the chamber from above the portion of the fuel bed of maximum thickness and subjecting the bottom of the fuel bed uniformly to air under pressure in excess of the highest pressure above the bed.

8. The method of burning fuel in a combustion chamber which includes admitting a bed of fuel of predetermined thickness to the chamber, progressively burning the fuel as it is conveyed through the chamber so that the thickness of the fuel bed and its resistance to the flow of air therethrough progressively diminish toward the region of complete combustion, passing the products of combustion along the fuel bed from the end thereof of minimum thickness toward the end of maximum thickness and at progressively increasing velocities with corresponding progressive decreases in pressure, said pressures decreasing proportionately as the resistance of the fuel bed to air flow increases, whereby a predetermined relation between the resistance to air flow of various portions of the fuel bed and the pressures thereabove is provided, withdrawing the products of combustion from the chamber from above the portion of the fuel bed of maximum thickness, subjecting the bottom of the fuel bed uniformly to air under pressure in excess of the highest pressure above the bed, and bleeding from the combustion chamber adjacent the portion of the fuel bed of minimum thickness, excess air in controlled quantities.

ROBERT A. FORESMAN. 

